Frequency-domain optical coherence tomography with extended field-of-view and reduction of aliasing artifacts

Abstract

The present disclosure provides an OCT imaging system to reduce or eliminate frequency-domain aliasing artifacts. The frequency is shifted using a carrier frequency to define a sampling range substantially centered on the carrier frequency. An image of the sample is generated from a displayed imaging range that consists of a subset of the frequencies within the sampling range. Furthermore, the system may be configured to determine the carrier frequency such that a Nyquist frequency corresponding to the shifted frequency is extended beyond either an upper or a lower bound of an OCT quality envelope corresponding to the first portion of light. Additionally, the carrier frequency may be determined such that a lower bound of the OCT quality envelope is greater or less than a zero-frequency DC limit.

What is claimed is: 
     
       1. A method for providing imaging information regarding a sample utilizing a frequency-domain optical coherence tomography (OCT) system, the method comprising:
 interfering a first portion of the electromagnetic radiation returning from the sample with a second portion of the electromagnetic radiation returning from a reference to generate an interfered radiation; 
 detecting the interfered radiation over a sampling range of frequencies each being associated with a different depth within the sample; and 
 associating optical information regarding first and second depths within the sample with first and second negative respective frequencies within the sampling range to generate the imaging information, wherein the first depths are greater than the second depths, and the second negative frequencies are more negative than the first negative frequencies, and wherein the sampling range (i) extends from one of the frequencies to another one of the frequencies, and (ii) is substantially centered on a carrier frequency. 
 
     
     
       2. The method according to  claim 1 , further comprising providing the carrier frequency with an optical frequency shifter using a fixed optical delay in at least one of (i) a sample portion of the electromagnetic radiation provided to the sample that is associated with the first portion, or (ii) a reference portion of the electromagnetic radiation provided to the reference associated with the second portion, so as to define the sampling range that includes a set of the frequencies. 
     
     
       3. The method according to  claim 1 , further comprising reversing a direction of the wavelength sweep of the electromagnetic radiation to provide the carrier frequency. 
     
     
       4. The method according to  claim 1 , further comprising providing the carrier frequency using a negative frequency shift in an acousto-optical frequency shifter. 
     
     
       5. The method according to  claim 1 , further comprising reversing a phase shift of at least one of the sample of the reference during an interaction of the first and second portions with one another. 
     
     
       6. The method according to  claim 1 , wherein the OCT system comprises (i) an optical source configured to generate the electromagnetic radiation over a range of wavelengths, and (ii) an interferometer configured to generate the interfered radiation over the sampling range of the frequencies associated with different depth within the sample. 
     
     
       7. A frequency-domain optical coherence tomography (OCT) system for providing imaging information regarding a sample, comprising:
 a wavelength-swept radiation source configured to illuminate (i) the sample with a first portion of an electromagnetic radiation, and (ii) a reference with a second portion of the electromagnetic radiation; 
 an interferometer configured to interfere a third portion of the electromagnetic radiation returning from the sample with a fourth portion of the electromagnetic radiation returning from a reference to generate an interfered radiation, the first and second portions are associated with the third and fourth portions, respectively; 
 an optical detector configured to detect the interfered radiation over a sampling range of frequencies each being associated with a different depth within the sample; and 
 a signal processor configured to associate optical information regarding first and second depths within the sample with first and second negative respective frequencies within the sampling range to generate the imaging information, wherein the first depths are greater than the second depths, and the second negative frequencies are more negative than the first negative frequencies, and wherein the sampling range (i) extends from one of the frequencies to another one of the frequencies, and (ii) is substantially centered on a carrier frequency. 
 
     
     
       8. The OCT system according to  claim 7 , further comprising an optical shifter configured to provide a fixed optical delay of the carrier frequency in at least one of the first portion or the second portion of the electromagnetic radiation so as to define the sampling range that includes a set of the frequencies. 
     
     
       9. The OCT system according to  claim 7 , further comprising a coupler configured to receive the electromagnetic radiation and reverse a direction of the wavelength sweep of the electromagnetic radiation to provide the carrier frequency. 
     
     
       10. The OCT system according to  claim 7 , further comprising an acousto-optical frequency shifter which is configured to provide the carrier frequency using a negative frequency shift. 
     
     
       11. The OCT system according to  claim 7 , further comprising a coupler configured to receive the electromagnetic radiation and reverse a phase shift of at least one of the sample of the reference during an interaction of the third and fourth portions with one another. 
     
     
       12. The OCT system according to  claim 7 , wherein the wavelength-swept radiation source is configured to generate the electromagnetic radiation over a range of wavelengths, and wherein the interferometer is configured to generate the interfered radiation over the sampling range of the frequencies associated with different depth within the sample.